Relationship between Solubility, Moisture Sorption Isotherms and Morphology of Chitosan/methylcellulose Films with Different Carbendazim Content

Dang Thi Mong Quyen, Joomwong Adisak, Pornchai Rachtanapun

Abstract

Chitosan and methylcellulose are popular biopolymer materials that are used in films and as coatings for food products. The addition of carbendazim which is an antimicrobial agent to these biopolymers can lead to changes in solubility, moisture sorption isotherm and the morphology of the chitosan/methylcellulose films (C/MC) at various carbendazim contents (0.8; 1.6; 3.2 and 4.8 g/100 g of solid C/MC). C/MC films with carbendazim had lower solubility values than control films. The moisture sorption isotherms of C/MC films incorporated with carbendazim were examined for water activities in the range of 0.11-0.86 at 25±0.5oC. These isotherms showed that carbendazim content affected the equilibrium moisture content (%EMC) of the films and the %EMC of all films dramatically increased above aw=0.66. The C/MC films incorporated with carbendazim exhibited lower %EMC than that of the control films under all relative humidity conditions. The changes of the moisture sorption isotherms of the C/MC films at different carbendazim contents can be related to changes in cross-section morphology of these films. By understanding the behavior of the sorption isotherms, it is possible to predict the moisture sorption properties of C/MC films via moisture sorption empirical models. The Guggenheim–Anderson–deBöer (GAB), Brunauer-Emett-Teller (BET) and Oswin sorption models were used to fit the experimental data. Our results show that the GAB model was the best-fit model for C/MC films incorporated with carbendazim at 25±0.5oC.

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